Emission node in 2.81 not working iun Cycles
There are multiple shader nodes that you can use to build materials. The "Principled BSDF" is an uber shader which gives a lot of options in a single node, one of which is emission. That shader will emit light when the color is changed to something other than black. If you want an image to be used as an emission light, plug the image into the color input on either the emission node or the principled bsdf, not both.